The IEEE standard 1532 describes an approach for in-system configuration of devices such as programmable logic devices (PLDs). The standard seeks to provide system designers with predictability of operations of configurable devices.
Part of the predictability includes describing the expected behavior of the device when it is incompletely configured. Example situations in which configuration may not complete include loss of power and signal interruption or electrical interference. When power is restored to the device, the user should not have to be concerned with damaging the device or system because of an incomplete configuration.
Among other requirements, the standard generally requires a device to assert an internally generated done signal after configuration is complete and hold the state of the done signal during the time that the device is operational. Based on the state of the done signal, damage to various components in the system may be avoided by aborting a power-up sequence if necessary.
The standard does not require, however, that the state of the done signal be associated with a correct configuration of the device, as compared to an incomplete configuration. Thus, there remains some risk that system damage might result when an improperly configured device asserts a done signal.
The present invention may address one or more of the above issues.